Electro-hydraulic flat forming system



Jan. 27, 1970 M. HUNDLEY ETAL. 3,491,564

ELECTRO-HYDRAULIC FLAT FORMING SYSTEM I Filed Nov. 24, 1967 3Sheets-Sheet 1- Marl #7 L. Hand/s y [c/w/n ,4. 77//, 4/7.

506/ 0, Fame lNI ENTORS /ITTORNE YS Jan. 27, 1970 Filed Nov. 24, 1967 M.L. HUNDLEY ETAL 3,491,564

ELECTRO-HYDRAULIC FLAT FORMING SYSTEM 5 Sheets-Sheet 2 fiz/e/ 0, FameINVENTORJ' /I TTORNE YS Jan. 27, 1970 M. L. HUNDLEY ETAL 3,491,564

ELECTRO"HYDRAULIC FLAT FORMING SYSTEM 3 Sheets-Sheet 5 Filed Nov. 24.1967 y e a 3 6 r R 2 M W 7 F u J E D 2 & ,7 /\V\/\ I W 0 N Z y 0 d. a ,BM f g ATTORNE YS United States Patent 3,491,564 ELECTRO-HYDRAULIC FLATFORMING SYSTEM Marvin L. Hundley, Edwin A. Till, Jr., and Buel 0.

Russell, Fort Worth, Tex., assignors to Electro-Form, Inc., Fort Worth,Tex., a corporation of Texas Filed Nov. 24, 1967, Ser. No. 685,535 Int.Cl. B21d 26/06 US. Cl. 72--56 Claims ABSTRACT OF THE DISCLOSURE Anelectro-hydraulic forming apparatusincluding upper and lower portionswhich are maintained in a closed position during the forming operationby trunnion mounte d clamps which wedgedly engage adjacent flanges ofthe upper and lower portions. The lower portion includes a firingchamber and electrode assembly. The firing chamber includes means foradding and draining an incompressible fluid and evacuating any gases inthe chamber while the two portions are in the closed position. Theelectrode assembly includes two or more electrodes positioned inside thechamber and means for moving the electrodes vertically Within thechamber.

BACKGROUND OF THE INVENTION This invention relates to apparatus forshaping workpieces of deformable material. More specifically, theinvention pertains to apparatus for shaping workpieces byelectro-hydraulic forming.

Electro-hydraulic forming refers to a method of forming a workpiece bydischarging electrical energy in a contained incompressible fluidmedium; The shock de veloped by the discharge is transmitted by thefluid to a workpiece which is suitably mounted in a forming die.

In a flat forming apparatus, a flat workpiece is positioned between adie portion and a container portion of the incompressible fluid.Electrodes are positioned in the fluid with a connecting wire which isdetonated by the electrical discharge. 1

The. two portions must be rigidly supported to prevent separationthereof by the shockwave developed by the electrical discharge. However,because of the extremely high pressure developed by the electricaldischarge, a suitable support presents a major problem. Hydrauliccylinders will not absorb the high pressures without some movement, andrigid clamps present problems in alignment.

Often it is desirable to use two or more discharges in forming oneworkpiece. To carry out the subsequent discharges, more fluid must beadded to accommodate the increased space ,due to the deformation of theworkpiece. Further, the fluid is often contaminated during theelectrical discharge and must be replaced before the next discharge.Also, since the discharge disintegrates the wire connecting theelectrodes, a new wire must'be provided for each electrode discharge.Replacing the wire is more difficult when the wire is submerged in'thefluid.

SUMMARY OF THE INVENTION In accordance with this invention anelectro-hydraulic forming apparatus is provided including novel dieassembly and die support means.

The die assembly has a lower portion which includes a fluid containerhaving a firing chamber filled with an incompressible fluid and in whichelectrodes are positioned and an upper portion which includes the die.Advantageously, the workpiece is supported above the incompressi-blefluid and the die is positioned above the workpiece. The two portionshave flanges which rnate when the portions are in a closed position.Trunnion mounted 3,491,564 Patented Jan. 27, 1970 die holding clampswedgedly engage tapered contact surfaces on the flanges and maintain thetwo portions in the closed position during the electro-formingoperation.

Two or more electrodes are provided in the bottom portion to carry outthe electrical discharges. The electrode assembly includes means formoving the electrodes vertically above the contained fluid, therebyfacilitating the attachment of wires to the electrodes without thenecessity of draining the fluid. Means are also provided to drain thefluid or add fluid to the apparatus after each electrical dischargewithout disassembling the apparatus.

Means are provided to apply pressure to the workpiece when the dieassembly is closed and thereby maintain a fluid tight seal during theforming of the workpiece.

The invention will be more fully understood from the followingdescription and appended claims when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a cross-sectional view ofone embodiment of the electro-forming apparatus with the die portion andsupport means in a raised position.

FIGURE 2 is a cross-sectional view of the apparatus of FIGURE 1 in aclosed position.

FIGURE 3 is a cross-sectional view of a workpiece after theelectro-forming operation.

FIGURE 4 is a cross-sectional view of the electrode assembly and seal.

FIGURE 5 is an isometric view of the actuating means for the dieclamping apparatus.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS Referring to thedrawings, and in particular to FIG- URE l and FIGURE 2, electro-formingapparatus in accordance with the invention is illustrated incross-section. In FIGURE 1, the upper portion including die retainingring 1 and die 2 is in a raised position. Die retaining ring 1 isattached to die holder platen 3 which is movably mounted on guide rods4. Pistons 5 of hydraulic cylinders 6 are connected to die holder platen3 and provide the movement of the upper portion along the rods 4.Hydraulic cylinders 7 are pivotably connected by pins 8 to supports 9depending from die holder platen 3. The rod 7a of hydraulic cylinder 7is also connected to retaining clamp 10 by pin means, thereby providinga trunnion mount for the clamp. Retaining clamp 10 slidably engages aguide 11 which also depends from the die holder platen 3, and theretaining clamp 10 is horizontally movable by means of hydrauliccylinder 7. The clamp and actuating means are further described belowwith reference to FIGURE 5.

The bottom portion of the apparatus includes retaining ring 12 which issupported by the base structure 13. A fluid container 18 having a firingchamber 19 is supported by retaining ring 12. The firing chamber 19 isshown partially filled with an incompressible electricallynon-conductive fluid such as water. The top surface of container 18 hasa recessed area 20 for accommodating a flat work piece. A vacuum port 22is provided in the container 18 to evacuate air from the firing chamber19 after a work piece is assembled and the upper portion is lowered toclose the apparatus. Fluid intake 23 and fluid drain 24 are alsoprovided in container 18 to circulate the fluid in the firing chamber 19as required. Electrode assembly 26 is mounted through the bottom ofcontainer 18 with coaxial electrodes 27, 28 and 29 positioned in thefiring chamber. The electrodes are in a raised position to facilitatethe attachment of wires 30 to the electrodes. The electrode assembly isdescribed in detail below with reference to FIGURE 4.

container 18. These cylinders function to maintain a pressure seal onthe work piece during the forming operation as shown in FIGURE 2.

In FIGURE 2, a work piece 35 is positioned in the recessed area 20 ofthe container and the upper portion of the apparatus is lowered by meansof hydraulic cylinders 6 until the die 2 abutts the work piece andflange 37 of the die retaining ring 1 are adjacent to flanges 38 of theretaining ring 12. The flanges have tapered contact surfaces which arewedgedly engaged by clamps 10. The trunnion mounting of hydrauliccylinder 7 to support 9 and the trunnion mounting of clamp 10 to the rodof cylinder 7 allow the clamp freedom of vertical pivotal movement andthereby effect proper alignment of the clamps in engaging the flanges.

After the apparatus is closed as shown in FIGURE 2,

the firing chamber 19 is completely filled with the incompressibleelectrically nonconductive fluid which is added through fluid intake 23.Air within the chamber is removed through vacuum port 22. A sealingpressure is maintained on the work piece by moving the fluid container18 upwardly by means of cylinders 32. Clamps 10 are maintained inpressure contact with the flanges of the retainer rings 1 and 12 bycylinders 7.

Prior to the forming operation the coaxial electrodes 27, 28 and 29 arelowered by the electrode assembly 26 as shown in FIGURE 2.

A large charge of current is then passed through wires 30 connectingelectrodes 28 and 29 to electrode 27. The current detonates the wireswhich effects a shock Wave that is transmitted to work piece by thecontained fluid. Typically, the electrical charge is in the order of100,000 joules and is released in a period of a few hundredmilliseconds. The discharge disintegrates the wires which must bereplaced before the next discharge between the two electrodes.

Should the fluid in the firing chamber 19 become contaminated after manyfirings, the fluid can be replaced, if necessary, by draining throughport 24 and adding new fluid through port 23.

FIGURE 3 is a cross section of work piece 23 after electroforming. Theconfiguration of the work piece is defined by the die.

FIGURE 4 is a cross-sectional view of the electrode actuator assembly 26and the coaxial electrodes 27, 28 and 29. The electrode actuatorassembly 26 consists of a head 48 which is slidably inserted in thelower portion of the fluid container 18 and suitably retained by boltsor the like. The head is sealed by O-ring 49 to prevent leakage of fluidfrom the firing chamber 19. Outer cylinder sleeve 50 is retained in head48 and sealed at that point by O-ring '51. End cap 52 is inserted in thelower end of sleeve 50 and threadably engages inner sleeve 54. O-ring 53seals the lower end of sleeve 50' at end cap 52, and inner cylindersleeve 54 is sealed at end cap 52 by O-ring 55. The upper end of innercylinder sleeve 54 threadably engages inner guide ring 56. Inner wiperring 57 i retained between the inner ring guide 56-and the innercylinder sleeve and is in slidable contact with the inside diameter ofthe piston sleeve 58. Piston sleeve 58 threadably engages piston sleevering 59 and is slid- In practieah application; the coaxialelectrodesare-inserted through the electrode; adaptor flange 65, the inner ringguide 56 and the endcap 52 and the flange 67 is attached to theelectrode adaptor flange 65 by screws or other suitable means.- Sealingis provided by O-rings 6 9, 70 and71. x v The'electrode assembly israised by air pressure applied at port'72 whichconsequently exhausts airfrom port 73. Conversely, the electrode assembly is lowered by applyingair pressure to port 73. The outer conductor tube'66 is long enough toallow full extension of the electrode assembly- Withinthe firingchamberwithout interferencewwith the ground conductor connector 74.

After the electrical discharge, wire 30 must be replaced. '=With thisnovel electrode assembly, the electrodes 27, 28and 29 are raised in thefiring chamber 19 above the contained fluid, and new wires are attachedwithout the necessity for draining the fluid. After the wires areattached, the'electrodes are again lowered until flange 65 abuts headmember 48 at the bottom of the firing chamber 19.-

FIGURE 5 is an isometric view of a portion of the electro-formingapparatus of FIGURE 1 and FIGURE ably movable between the inner andouter cylinder sleeves. v

Piston sleeve ring 59 is sealed by O-rings 60 and 61. Piston sleeve 58contacts head 48 and is sealed by means of O-ring 62. Wiper retainerplate 63 retains wiper ring 64 which is in slideable contact with theoutside diameter of piston sleeve 58. Electrode adaptor flange 65threadably engages the upper end of the piston sleeve 58.

The coaxial electrodes consist of an outer conductor tube 66 andflange67, which comprise a unitary structure, and electrodes 28 and 29 whichare threadably or otherwise attached to flange 67. A centerelectrode 27is positioned in the center of the outer conductor tube 66 and isinsulated therefrom by a suitable insulation material 68.

2, and further illustrates the trunnion mounting of hydraulic'cylinder 7to the support 9 depending from die holder platen 3. Pin 8 connects thecylinder to the support, and allows the cylinder to have freedom ofvertical pivotal motion. The trunnion mounting of the cylinder tosupport 9 along with the trunnion mounting of the cylinder rod to clamp10 (not shown) enables the clamp 10 to, seek proper alignment when movedto engage the tapered flanges on die retainingring 1 and retaining ring12 as shown in FIGURE 2. Thus critical tolerances can be maintained withthis apparatus since the clamp is properly aligned when engaging theflanges.

While the invention has been described with reference to specificembodiments, the description is illustrative and is not to be construedas limiting the scope of the invention. Various modifications andchanges-may occur to those skilled in the art without departing from thescope of the invention as defined by the appended .claims.

What is claimed is:

1. An electrohydraulic forming apparatus comprisung: e

an upper die adapted for vertical movement and having an outer flangewith tapered upper surface;

a lower firing chamber member having an outer flange with a taperedlower surface, said lower firing chamber member being adapted to hold anincompressible fluid and to close with said die member to hold the workpiece therebetween;

means for initiating an explosive pulse in said firing chamber member;

clamp means comprising a plurality of C-clamps having inner clampingsurfaces adapted to wedgedly engage the tapered surfaces of said outerflanges on said die -member and firing chamber member;

means mounting each of said C-clamps for limited pivotal motion in avertical plane;

means to actuate said clamp means into engagement 7 with said flanges;and

means for applying pressure between said firing chamber and said diemember in addition to pressure exerted by said clamp means to hold awork piece therebetween. I I

2. The apparatus of claim 1 wherein said ,means for initiating anexplosive pulse includes:

a first electrode extending into said firing chamber;

a second electrode insulated from said first electrode and disposedaxially about saidfirst electrode; 1

an explodable wire disposed between said. electrode;

and

means to raise said first and second electrodes with respect to saidfiring chamber member to enable replacement of said wire after use.

3. The apparatus of claim 2 including a support member within saidfiring chamber for supporting said electrodes and an air cylindermounted vertically .through said firing chamber member including astationary inner sleeve, a stationary outer sleeve, and a movable pistonsleeve between said inner and outer .sleeves, said movable piston sleevebeing attached to said support member to raise and lower said supportmember .and said electrodes.

1 4. The apparatus of claim 1 including means immediately below saidWork piece to evacuate gas from said firing chamber member between saidwork piece and said incompressible fluid when said work piece is in.place to permit filling said chamber completely with .suchincompressible fiuid when the work piece is in ,position.

i S. The apparatus of claim 1 wherein said means for .applying pressurebetween said firing chamber member and said die member comprise aplurality of hydraulic cylinders disposed below said firing chambermember and adapted to exert upward pressure on said firing chambermember against said die member.

References Cited UNITED STATES PATENTS RICHARD J. HERBST, PrimaryExaminer

